There are numerous instances where persons desire enlargement of the soft tissues in their bodies. One such instance is for the replacement of one or both breasts amputated during a mastectomy in order to restore physiological symmetry and psychological well-being. Other instances are for correction of natural abnormalities such as dimpling. Still other instances are for augmentation of physical attributes to improve cosmetics and self-esteem. These latter soft tissue enlargements are principally directed to breast enlargement in females and penis enlargement in males.
Prosthetic implants have been developed for insertion below the skin. However, the severity of the potential complications including scarring, implant rupture, capsular contracture, necrosis and implant migration as well as the recent adverse publicity thereof have significantly reduced the desirability of these implants. Thus, there is a societal need for other means to obtain soft tissue enlargement.
Some soft tissue enlargements occur naturally. For instance, during pregnancy, the skin over a woman's abdominal region enlarges approximately nine times its previous area to accommodate the fetus without a proportional decrease in skin thickness. In other words, the abdominal skin tissue actually enlarges and does not merely stretch during pregnancy. Similarly, the skin will expand to accommodate any growth under the skin.
In the past, plastic surgeons have used this phenomenon to their advantage to expand skin in order to accommodate prosthetic implants. To conduct this procedure, the surgeon inserts a balloon beneath the skin in the area where additional skin is desired. By progressively expanding the balloon, the skin first stretches and eventually actually grows to accommodate the increased volume underneath it. When the desired amount of skin is formed, the balloon is deflated and removed, and the implant is inserted into the cavity left by the balloon. Similar methods have been used by native African tribes to enlarge lips, nostrils, and earlobes.
Other surgical techniques have used tissue expansion to achieve other types of soft tissue growth. For instance, balloons have been successfully expanded underneath nerves, veins, tendons, and the like to thereby elongate these tissues to repair damage and alleviate various abnormalities.
A more advanced surgical method is known as callotasis or limb lengthening. This method comprises cutting the bone about its periphery at the location where lengthening is desired, leaving the tissues inside and around the bone intact. Brackets are attached to the bone on each side of the separation, and the bone segments are slowly pulled away from one another while remaining integral over a period of several months. Not only does this cause the mended bone to be longer, but also the soft tissue surrounding the bone actually grows to accommodate the increased limb length. Similar methods have been used by African native tribes to lengthen necks for cosmetic purposes.
Each of these above-mentioned apparatuses and methods requires an invasive surgical technique to accomplish the soft tissue expansion. Invasive techniques increase the likelihood of the complications associated with the procedure including those mentioned above with respect to implant surgery. In addition, the expense of surgery precludes many persons from having their abnormalities corrected or physical attributes enhanced.
Other soft tissue enlargement techniques have been developed which use other mechanisms to cause the enlargement. For instance, an instrument and technique have been developed for the non-surgical correction of inverted nipples due to short lactiferous ducts. The instrument is comprised of a cup having an internal volume shaped like that of the final desired nipple. The user places the cup over the inverted nipple, pumps the air out of the cup with a syringe and adjusts the vacuum within the cup using a check valve to just below the threshold of discomfort. Thus attached, the device puts he lactiferous ducts in tension and extends them sufficiently after two to three months of wear at 8-12 hours per day.
Although this device is sufficient for its intended purpose, it is not suitable for general soft tissue enlargement. Laceration and contusion can occur if too strong of a suction is applied to soft tissue. As the pressure within the inverted nipple instrument is not regulated, contusion or laceration can occur. When a vacuum is developed within the cup of the instrument, an equal and opposite force is applied to the patient about the rim of the cup. Excessive contact forces against the patient can cause ulceration, laceration, and contusions. As the contact forces are not regulated in the nipple instrument, these further complications also can occur. In addition, general soft tissue enlargement is not feasible with the instrument due to the size and shape of the cup.
Another prior art device is disclosed in U.S. Pat. No. 936,434 as a device for enlarging a woman's breasts. This device included a pair of cups for placement on the breasts and a pump for exhausting the air from between the cups and breasts. However, this patent provides no teaching as to the pressures to be used, the potential danger to the skin tissues, or any suggestions as to how the device is to be retained in place during use. Apparently, the device is used in a clinical setting and is not suitable for long term wear such as for 8-10 hours. As the patent suggests that the vacuum acts to cause the veins and arteries to engorge, thereby nourishing the breasts, it is clear that the patentee is suggesting that the breast tissue actually expands through this expansion of blood vessels alone. This patent has been the subject of ridicule by at least one medical authority. See "An Anthology Of Plastic Surgery" edited by Harry Hayes, Jr., M.D., Section 6, "Quackery and Nostrums" pub. 1986 by Aspen Publishers, Rockville, Md.
Another prior art device although notorious is worthy of note. This device is commonly referred to as a penis pump and is sold primarily as a novelty as its long-term enlargement efficacy has never been proven and is in fact universally disclaimed by its distributors. The device is comprised of a cylinder having one open end into which the penis is inserted and a pump attached to it such that a vacuum can be created within the cylinder. Not only does this device have the same drawbacks as the nipple instrument with respect to potential complications, but also it is unlikely that sufficient vacuum can be maintained by the device to cause any notable long-term soft tissue enlargement. Further, this device is apparently designed to accomplish two tasks unrelated to enlargement. First, the device is used for stimulation and sexual gratification. Second, the device is used to promote erection by drawing blood into the penis.
Most of these prior art devices and methods have failed to achieve long term soft tissue enlargement while preventing damage to the soft tissue being enlarged, as well as surrounding tissue. As disclosed and claimed in the parent applications noted above, the inventor herein has succeeded in designing and developing a new generalized method and apparatus for soft tissue enlargement which prevents damage to soft tissue. The apparatus used for this enlargement is comprised of a rigid, fluid-impervious dome having a rim about its periphery and a vacuum pump for reducing pressure within the dome. The rim has sufficient surface area such that the pressure applied to the patient by the rim is less than or equal to the negative pressure applied to the soft tissue under the dome. In the parent applications, one specific teaching to achieve this balanced force utilized a rim with substantially the same cross-sectional area as the normal area of the dome. Thus, as long as pressure within the dome is regulated to a limit below which medical complications will not occur, the opposing contact pressure against the patient is below this threshold as well. With this approach, damage is avoided not only to the soft tissue being enlarged, but the surrounding tissue as well. In the preferred embodiment of the apparatus, the vacuum pump has a self-contained power source. In addition, a pressure sensor and servomechanism control the pump such that the vacuum within the dome is maintained at a magnitude less than 35 mmHg. Variant embodiments may be configured to fit over and enlarge a human breast, a human penis, or any other desired area.
In still another patent application filed on behalf of the present inventor entitled "Method And Apparatus For Promoting Soft Tissue Enlargement and Wound Healing" having Ser. No. 08/408,423 filed Mar. 22, 1995, the present inventor disclosed and claimed an invention which utilizes a rigid fluid-impervious dome having a rim about its periphery and a vacuum pump for reducing pressure to thereby apply a distracting force to the soft tissue isolated by and within the dome. The dome may be conveniently located over an open wound in order to promote healing of the wound by enlarging the soft tissue under the dome. As the soft tissue grows, it promotes healing of the wound through acceleration of the closing thereof by soft tissue growth. As wounds may be received by a patient to any part of his body, the inventor's prior disclosed and claimed invention includes the use of a dome over virtually any part of the human body.
In implementing these prior inventions, the inventor intends that it be capable of achieving its therapeutic effect without creating any long term tissue necrosis from use. In other words, a vacuum must be applied to the desired area to achieve the therapeutic effect for sufficient periods of time without applying too great a vacuum or contact pressure which will damage the underlying tissue. As considered from this generalized approach, one of ordinary skill in the art would understand the inventor's teaching to include the idea of providing a smaller vacuum pressure within the dome and balancing that smaller vacuum with a rim having a surface area less than the normal area of the dome, thereby creating a greater contact pressure which is still within acceptable limits. Still another approach which may very well provide a therapeutic effect would be to cycle the vacuum in the dome such that it is applied for periods of time at elevated levels and relaxed levels so that the rim might also have a cross-sectional area less than the normal area of the dome, but yet avoid creating any tissue necrosis. The cycling of the vacuum pressure in the dome could be readily achieved in an automatic manner by appropriately programming the vacuum pump and regulator. Therefore, the invention should be understood as being limited only by the current medical understanding of the causative effects of pressure sores and other tissue damage by an applied pressure or vacuum.
It is well recognized in the medical literature that decubitus ulcers are caused by unrelieved external pressure that occludes blood flow and results in tissue necrosis. In recognition of this fact, these ulcers are called pressure sores. The average capillary pressure in human skin is around 15-20 mmHg. E. M. Landis, Micro-Injection Studies of Capillary Blood Pressure in Human Skin, 15 Heart 209-228, (1930). For convenience, 20 mmHg will be used to describe this pressure throughout the remainder of this description. However, it should be understood that pressures below 20 mmHg may also be used without departing from the scope of this invention and that these lower pressures may provide additional margins in preventing damage to tissues. Therefore, the local application of an external pressure up to 20 mmHg will not collapse capillaries adjacent the location of the applied pressure and thus will not disturb the circulation. Therefore, local application of contact pressures less than or equal to 20 mmHg are well tolerated for prolonged periods of time. This tolerance has been confirmed by the inventor through use of a prototype which did not cause adverse effects after many hours of continuous use as long as the pressure under the rim remained below or around 20 mmHg.
Pressures greater than 20 mmHg will occlude the capillaries and stop tissue perfusion. Tissues can tolerate short periods of ischemia, but if the pressure is continuous and perfusion is not restored within a relatively short period of time, tissue damage will ensue. "The time factor is thus more important than pressure intensity". A pressure of 100 mmHg will lead to pathologic changes after only two hours. T. Hussain, An Experimental Study of Some Pressure Effects on Tissues, with Reference to the Bed-Sore Problem, 66 J. Path. Bact. 347-358, (1953).
The experimental results of additional investigators can be used to develop a safe time-pressure curve above which tissue damage will ensue. For instance, 20 mmHg is well tolerated for prolonged periods of time, but 40 mmHg will lead to tissue injury if the pressure is not relieved for 13 hours. The injury is more severe if the pressure is 60 mmHg, and even greater injury will result with a pressure of 100 mmHg after shorter periods of time. O. Lindan, Etiology of Decubitus Ulcers: An Experimental Study, 42 Arch. Phys. Med. Rehab. 774-783, (1961). Similarly, a pressure of 70 mmHg, if unrelieved, will lead to pathologic changes after 2 hours. However, if the pressure is intermittent, applied 5 minutes on, and 5 minutes off, there is no pathologic tissue changes. M. Kosiak, Etioloqy of Decubitus Ulcers, 42 Arch. Phys. Med. Rehab. 19-29, (1961).
These findings are consistent with the clinical testing of the prototype of the breast device. It was found that a continuous pressure under the rim of 40 mmHg could be tolerated for only one hour by healthy volunteers. After one hour, the volunteers started to complain of pain which is the warning sign of impending tissue damage. Higher pressures led to pain under the rim after even shorter periods of time. Lower pressures around 30 mmHg led to pain after 4 hours. However, if the pressure is allowed to cycle, that is if it is dropped down to 0-20 mmHg to allow the tissues to temporarily reperfuse for a few minutes, higher peak pressures can be tolerated. The higher the peak pressures, the shorter they are tolerated and the longer the low pressure part of the cycle needs to be to allow the tissues to recuperate.
Therefore, pressures under the rim greater than 20 mmHg can only be tolerated if there is a means to continuously cycle the pressure peaks on and off allowing for tissue re-perfusion during the off periods. The higher the peaks, the shorter the pressures are tolerated and the longer the period of low pressure recuperation needs to be.
From the above experimental animal data and human study, the inventor concludes that 20 mmHg is the highest pressure that can be safely tolerated under the rim on a prolonged basis. Higher pressures can only be applied intermittently, and then cycled down to less than 20 mmHg.
The method of use is comprised of the steps of attaching the dome to the location of desired enlargement, and creating a vacuum within the dome. In the continuous application method in which the vacuum is applied at pressures that can be withstood continuously, the vacuum should be maintained for a minimum of eight hours per day and results should be sufficient after several months.
As indicated by the summary of the medical literature given above, a vacuum dome may also be used in alternative methods in keeping within the scope of the inventor's concept. For example, the device might have a rim cross-sectional area substantially less than the normal area of the dome and be used in either of two methods. In a first method, a somewhat lower vacuum pressure may be induced in the dome such that the opposing contact pressure under the rim may be maintained at bearable pressures for extended periods of time and yet provide a therapeutic effect. Alternatively, the vacuum in the dome may be regulated in a routine which provides somewhat higher vacuum pressures in the dome for shortened periods of time separated by periods of lower vacuum pressures to allow tissue reperfusion. In other words, alternating cycles of high vacuum, tissue reperfusion, high vacuum, tissue reperfusion, etc., may achieve a therapeutic effect in enlarging the soft tissues. With either of these methods, the rim may have a cross-sectional area substantially less than the normal area of the dome.
In an alternate embodiment, the dome may include a flexible sheet attached about the rim and spanning the dome. The sheet may be applied to the desired soft tissue with an adhesive, and the vacuum may be applied between the dome and the sheet to introduce a tensile force to the surface of the soft tissue so as to pull the soft tissue away from the body. The adhesive may comprise typical adhesives or glues, as well as, sticky gels or sheets of double-sided adhesive tapes. Further, the adhesive may be an adhesive substance embedded in the sheet or in the rim of the dome.
In addition to the embodiments already discussed, the inventor has conceived of additional embodiments which further utilize the vacuum dome. One such embodiment is especially useful in the healing or reconstruction of amputation stumps. Whether the amputation is exemplified by an acute open wound (e.g. fingertip amputations) or an extremity amputation stump that tends to break down because of a deficiency in soft tissue padding, the growing of soft tissue may be especially advantageous in healing these wounds and adding tissue padding to what might otherwise become a chronic wound particularly susceptible to infection. In this application, the vacuum dome is supported around the amputation stump, much as taught in the inventor's prior disclosures, and maintained using an appropriate protocol to encourage the growth of soft tissue. Still another newly conceived application for the vacuum dome is as an aid in endoscopic or other minimally invasive surgery. In this application, a vacuum dome may be placed over a skin surface and used as an external retractor to lift up the surface integument to thereby create an optical cavity for subcutaneous endoscopic surgery. A pressure differential introduced within the dome may be used to separate the skin from the underlying tissue without interfering with either surgical access or viewing by the surgeon during the procedure. As such, this application for the vacuum dome provides distinctive advantage over several of the prior art approaches including the use of balloons to gently separate the skin from the underlying tissue. When in place, the balloon obviously interferes with surgical access and obscures surgical viewing. Applying a vacuum to the skin to encourage its separation may be done externally and thereby leave clear access in sight to the surgical point of contact.
In implementing any of the embodiments of these prior inventions, the inventor utilizes a dome which is positioned adjacent a skin surface and which requires an airtight seal between the dome and the skin surface. In several of these embodiments, a vacuum may be drawn within the dome as well. In utilizing this construction, the inventor is aware of potential complications which can develop when an area of the body needs to be enclosed for prolonged periods of time within the dome having an airtight seal. For example, while a rim made of conforming or other soft materials may suffice for temporary use, a number of problems arise in the skin contact area when prolonged negative pressure application is necessary. The present invention includes in its various aspects various features which are intended to deal with these problems.
One such concern is for the management of the shear forces generated by the dynamic inward pull of the skin. As explained above, drawing a vacuum within the dome creates dynamic forces under the rim of the dome as the skin and other soft tissue is "pulled" up into the dome by the vacuum. Generally speaking, these forces place a shear force on the skin which has been found to be roughly equivalent to a normal force in that the skin blood flow decreased roughly linearly with the increase of shear forces. See the effect of shear forces externally applied to skin surface on underlying tissues by Zhang and Roberts, Journal of Biomedical Engineering, Vol. 15, No. 1, January 1993, pages 451-456. The effect of these shear forces may be dramatically minimized by providing an interface between the dome and the skin which allows inward displacement of the contact surface in response to the vacuum. There are numerous examples of structures which could achieve this desired inward displacement including a gel, an inflatable bladder, a bellows, a corrugated collapsible structure, or virtually any other mechanical/geometrical design which will allow substantially inward concentric movement of the contact surface area.
Still another problem encountered in applying a dome to a skin surface is the possibility for tissue damage at points of pressure concentration. It is well known from the literature on pressure sores that the body has numerous pressure points where bony prominences lack the thick layer of soft tissue padding needed to dissipate the pressure subjected to the overlying skin. These are the prominences where pressure sores tend to develop. Furthermore, with movement of the body parts, these pressure points are not static and fixed but have a tendency to shift from one cutaneous area to the other. To avoid creating points of pressure concentration at these shifting surfaces over bony prominences, it is important for the cushion under the dome to be able to constantly and evenly distribute the pressure on its underlying skin. This even distribution may be provided by a rim on the dome that has fluid-like properties. This cushion could be constructed with an air or fluid bladder, or any other type of membrane containing a gel-like fluid. Still other equivalent structures could be envisioned to achieve the same effect such as the use of a gel-like substance that can retain its contour and shape without a membrane layer boundary. This gel-like substance would approximate the hydraulic effect of a fluid-filled bladder.
A related problem to that of shifting points of pressure concentration is the overall contour of the body surface underlying the rim. This is especially the case as a wearer of the dome performs his routine daily activities. These routine daily activities would ordinarily shift the dome and would potentially cause the dome rim to contact other areas of the body not having the same contour as at the "at rest" orientation. For these reasons, the rim should be designed to constantly accommodate a potentially ever-changing contour for the underlying body surface. To achieve this, the rim should be flexible and have a surface with mechanical bending properties approximating those of the underlying body tissue. This may be achieved by using a cushion having the fluid-like properties as described above to accommodate pressure concentration caused by bony prominences.
Another significant consideration in utilizing a dome in the various inventions developed by the inventor herein is the requirement that an airtight seal be maintained to preserve minimal to small vacuum pressure differentials. Escaping air at the interface between the rim and the skin leads to loss of vacuum and necessitates frequent activation of a pressure pump. This is undesirable in that it is at best a nuisance. Loss of vacuum is untenable for a truly portable device which would require a portable pump and power supply. In any event, the integrity of the seal between the rim and the skin directly impacts on the useability and performance of the vacuum dome. Ideally, a cushion may be utilized under the rim and between it and the skin to provide an airtight seal without an excessive force being applied as excessive forces may themselves create tissue damage. A heightened seal integrity may be achieved through the use of a "sticky" material which may be placed under the cushion or surrounding the cushion so as to adhere and bond to the skin a surface which preserves the pressure integrity. This "sticky" aspect of the present invention may be achieved by utilizing a material for the cushion itself which has a sticky, gooey, gluey, or gummy surface property. Numerous materials including polymers such as silicone, hydrogels, and many other low durometer synthetic rubbers and gels have this inherent surface property. A sheet or layer of this "sticky" polymer or other material may be added as a skin surface contact sole to the undersurface of the cushion for the rim, with the cushion itself not exhibiting this "sticky" property. Still another alternative is a skin adhesive layer which can be painted, sprayed, or otherwise applied to the lower surface of the cushion intended to contact the patient's skin. Again, this would essentially form a "sole" for the rim cushion. Still another methodology may consist of applying a layer of adhesive by painting, spraying, or otherwise adhering a gluey or sticky surface directly to the skin itself. A "sticky" tape may be used as the sole or even a double-sided sticky skin tape can be provided to interface between the rim cushion and the skin. Those of ordinary skill in the art could conceive of other ways to achieve this "sticky" contact between the dome and the underlying skin in order to maintain the integrity of the seal. Furthermore, the combination of the relatively hard rim that can distribute the counter-pressures evenly along its width with the underlying cushion of gel or fluid-filled bladder when combined with the adhesive "sticky" sole for maintaining the integrity of an airtight seal can be blurred and yet be covered by the inventor's inventive concepts. For example, these advantages may all be achieved through structure constructed out of the same material with a gradient of tackiness or durometer properties.
While the practical advantages and features of the present invention and method have been briefly described above, a greater understanding of the novel and unique features of the invention may be obtained by referring to the drawings and Detailed Description of the Preferred embodiment which follow.